`test` and `[` - different binaries, any difference?

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http://unix.stackexchange.com – I noticed while answering another question that test and [ are different binaries, but the [ manpage pulls up test's. Besides the requirement for an ending ], is there any difference? If not, why are they separate binaries instead of being symlinked? (They are also bash builtins, and bash doesn't show a difference either.) (HowTos)